This application claims the priority of International Application No. PCT/DE2007/000916, filed May 18, 2007, and German Patent Document No. 10 2006 024 085.5, filed May 23, 2006, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a turbo compressor in an axial type of construction for a gas turbine, having a bladed stator and a bladed rotor, wherein the stator is comprised of a compressor casing that is longitudinally split on diametrically opposed sides and at least one guide blade ring with adjustable guide blades.
In the case of turbo compressors in an axial type of construction for gas turbines, in principle a differentiation is made between two designs with respect to the casing construction. There is a longitudinally split compressor casing with two diametrically opposed, axial-running parting lines, which are able to be dismantled into two “half shells.” This design is also called “split case.” In addition, there is also a transversely split compressor casing, which is made up of several concentric casing rings that are lined up axially in a row. As a rule, the casing rings are screwed to one another via flanges pointing radially outwardly. Both designs have specific advantages and disadvantages and may also be combined in the case of multi-stage compressors having a considerable axial extension.
The case at hand deals with compressors or compressor modules having a longitudinally split casing, i.e., the “split case” design, which offers advantages with respect to lightweight construction and ease of assembly.
Furthermore, these should be compressors which have a minimum of a guide blade ring with adjustable guide blades. These types of compressors may be better adapted to changing operating conditions, this with a low number of stages, small construction volume and low weight. It is common to position adjustable guide blades radially outside the aerofoil on or in the compressor casing, radially within the aerofoil on or in an inner ring belonging to the stator. For this purpose, the guide blades emanating from the aerofoil have an outer peg that is longer as a rule along with an inner peg that is shorter as a rule. On the aerofoil/peg transition, there is often a plate-like disk which has flow-related and mechanical functions. The static inner ring, whose radially outer surface forms a portion of the inner ring space delimitation, features for every guide blade a complementary indentation for the inner, plate-like disk on the guide blade as well as a bearing for the inner peg. As a rule, the bearing is designed as a sliding bearing with a radially oriented longitudinal center axis. The inner ring is transversely split, wherein the parting line runs through the longitudinal center of the bearing. In addition, the inner ring is longitudinally split on two diametrically opposed sides so that for all intents and purposes it is comprised of four half rings, two of which respectively abut axially and are normally screwed together. Thus, it is possible to install the guide blades in the separate compressor casing halves and then mount the inner ring with the bearing for the inner pegs. In this case, for every compressor casing half, two half rings of the inner ring axially are moved against one another over the freestanding inner pegs and the plate-like disks of the guide blades until they touch in the target position and are then screwed together. In this connection, the inner ring parts themselves are often already provided with a rub coating or run-in coating, which cooperates with circumferential fins (fins) so that it seals on the rotor (inner airseal). There are disadvantages to this inner ring construction in accordance with the prior art. The mechanical stability and the end precision are not optimal because of the transverse split and screw connection. The radial and axial dimensions are larger as a rule in relation to a monolithic component, which has implications for the rotor dimensioning. The local rotor diameter must be reduced, and in addition the rotor length increases under some circumstances. Both have disadvantages for the dynamic rotor behavior (rigidity, oscillation behavior, weight, etc.) The parts of the screw connection are able to detach during operation and produce serious damage. Because of the transverse split, the parting line impacts the position and extension of the run-in coating, because the line extends over the entire circumference of the inner ring. Due to its complexity, this design is also very expensive.
On the other hand, the objective of the invention, in the case of a turbo compressor of the type cited at the outset with adjustable guide blades, is optimizing the inner ring, which is positioned in the area of the inner airseal and the rotor, and supports the guide blades in this area, with respect to its mechanical properties, its construction volume, its weight and its ease of assembly in order to ultimately also improve rotor dynamics.
In adapting to the longitudinally split compressor casing, the inner ring is also split, i.e., segmented, at at least two points of its circumference. Each of its at least two segments is one-piece, i.e., monolithic. The inner ring has in its segments for each of the adjustable guide blades at least one bearing bush which may be inserted radially into an opening from inside. Starting from a state in which the adjustable guide blades are already inserted in the dismantled compressor casing halves, and the aerofoils' inner pegs serving as the inner bearing freely project inwardly, the segments may still be moved without bearing bushes radially from inside with their openings for the bearing bushes beginning on one segment end over the inner pegs. Through progressive feed-in, more and more openings move over the inner pegs until all inner pegs are sitting in the openings of the segment assigned to them. This mounting procedure utilizes the fact that the openings in the segments are considerably larger in terms of the diameter than the inner pegs so that the latter may be positioned temporarily eccentrically and diagonally in the openings.
The bearing bushes may then be inserted radially from the inside into the segment situated in the target position, wherein one or more bushes may be provided per bearing, i.e., per inner peg and opening. The as such monolithic segments are optimal in terms of strength, construction space and weight and do not require any additional elements such as screws, nuts, pins, etc., which are detachable. As expendable parts, the bearing bushes may be replaced without the segments of the inner ring or the guide blades having to be disassembled.
A sealing support with a rub coating or run-in coating should preferably be detachably fastened on the inner ring. The sealing support, like the inner ring itself, should be segmented and be held on the inner ring in a radially form-fit manner as a sheet metal profile.